What is the wavelength of light emitted when the electron in a hydrogen atom undergoes transition from an energy level with n = 4 to an energy level with n = 2?
The ni = 4 to nf = 2 transition will give rise to a spectral line of the Balmer series. The energy involved in the transition is given by the relation,
E=2.18×10−18[1n2i−1n2f]
Substituting the values in the given expression of E:
E=2.18×10−18[142−122]=2.18×10−18[1−416]=2.18×10−18×(−316)
E = – (4.0875 × 10–19 J)
The negative sign indicates the energy of emission.
Wavelength of light emitted (λ)=hcE(since E=hcλ)
Substituting the values in the given expression of λ:
λ=(6.626×10−34)(3×108)4.0875×10−19λ=4.8631×10−7mλ=4.8631×10−9mλ=486nm